In order to determine the structural changes inside the membranes of nerves and surrounding glia during degeneration and regeneration, the ventral nerve cord of crayfish was chosen because of its accessibility, and therefore, minimal scarring after the cord is sectioned. In intact animals and in those with sectioned roots, the nerve roots were either soaked in peroxidase (HRP) or freeze-fractured. In both normal and degenerating roots, a hitherto unsuspected system of transglial channels accessible to HRP has been recognized in both thin plastic sections and freeze-fracture replicas. The channels, about 240 A wide, are straight and short, being as long as the thin glial sheets are wide. The frequency is about 16 per micron m2 in both normal and degenerating areas. In replicas, the channel openings appear as circular depressions or protuberances. In degenerating roots, the glial cells become disorganized but still lie close to axons. The gap junctions between glial cells increase in number but diminish in size. The observations signify that in the ventral cord, transglial channels may provide extracellular short-cuts whereby water, ions and metabolites move quickly from interstitial fluid to axonal membranes. The observations raise the question of whether shortened diffusion pathways permeate glial scars in mammals.